The present invention relates generally to roping configurations for elevators.
Elevators and their associated mechanical components are well known. Elevators are used to move people and equipment between floors in multistory buildings. A conventional traction type elevator installation includes an elevator car mounted in a car frame and moveable in a hoistway, a counterweight attached to the car via a rope, and a machine driving a traction or drive sheave that is engaged with the rope. As the machine turns the drive sheave, friction forces between the surface of the sheave and the rope move the rope and thereby cause the car and counterweight to raise and lower in opposite directions. The rope also can be routed through various turning or diverting sheaves when the drive sheave is not positioned directly above the car and the counterweight.
The mechanical components of the conventional elevator drive are generally located in a machine room, which room can be located at the top or bottom or to the side of the hoistway. Advances in elevator technology have led to the development of machine-room-less (MRL) elevator installations. As this name implies, this type of elevator mechanical system does not employ machine rooms at all. The MRL elevator applications have the goal of reducing the amount of building space occupied by the elevator systems, thereby increasing the amount of usable space on the floors.
As these MRL elevator installations become more common, a problem that arises with them, however, is that the elevator car and counterweight must be suspended within the hoistway in a different manner than in prior art elevator installations having machine rooms. For example, in order for MRL types of elevators to achieve minimum overhead requirements, small permanent magnet gearless machines are typically required. This is in contrast to the traditional elevator arrangements with machine room geared applications, where a large diameter traction sheave, which has ample tractive capabilities, can be used. This traditional arrangement can operate adequately with a one-to-one roping arrangement at less than 180 degrees wrapping of the ropes around the drive sheave, which allows for the use of a deflector sheave to achieve the desired location of rope drops even though the wrapping on the drive sheave is less than 180 degrees.
However, the small machines employed in MRL applications tend to require small sheave diameters for the drive sheaves. With these smaller sheave diameters, a full 180 degree wrap is needed with a two-to-one roping arrangement. In order to accommodate these needs with conventional steel suspension ropes, the elevator configurations tend to require a configuration with the counter weight mounted on the side of the elevator car. But a side mounted counter weight configuration creates hoistway packaging issues in certain standard sized hoistways that are designed for front opening elevators with rear located counter weights. To overcome this, some are employing belts or synthetic (for example, aramid) ropes, which can allow for configurations with more total and more severe bends without adversely affecting the rope life. These bends in conventional steel suspension ropes may not be particularly desirable. Thus, these configurations may limit the choice of the type of roping employed in the elevator installation.
It is desirable, therefore, to improve upon the configuration of the suspension rope and sheaves in MRL configurations of traction-type elevator installations that will allow for rear mounted counterweights, while not being too limiting of the type of roping employed.